Upper limb functional testing in athletes: A Delphi study.

Background: Functional testing has recently become more and more popular to assess athletes, both for injury prevention, as well as in an objective of performance. However, the relationship between the results of these tests and performances (or injuries) or their interpretation remains unclear. Objective: The aim of this study is to explore the usefulness, the characteristics, and the interpretation of the most frequently used upper-limb functional test. Methods: Twenty-two experts with an excellent knowledge of upper limb functional tests and an expertise in sports medicine and/or sports training of at least 5 years were recruited. They answered to qualitative and quantitative questions about functional testing trough structured questionnaires (online). Results: Four rounds were needed to reach a consensus about the usefulness as well as the characteristics of each test. Different sports-specific batteries of tests were also suggested by the experts and reached consensus. However, concerning the interpretation of the test, a consensus was only found for half of the tests considered. Conclusion: The current study summarizes the characteristics and the usefulness of the most popular upper-limb functional tests. However, the interpretation of some tests will have to be further explored since no consensus was found for them.

Continuous suprascapular nerve blockade to potentiate intensive rehabilitation for refractory adhesive shoulder capsulitis: a cohort study.

PURPOSE: Evaluating the short- and long-term efficacy of a continuous ten day suprascapular nerve block combined with daily multidisciplinary rehabilitation on shoulder range of motion (ROM), pain, and function in patients with refractory adhesive capsulitis (AC). METHODS: In this retrospective cohort study, patients admitted to a specialized pain clinic for refractory AC for more than 6 months underwent continuous suprascapular nerve blockade for ten days and received 2 hours of physiotherapy and occupational therapy daily. Standardized assessments were performed at baseline, at days three, six, ten, 30, 90, and 180, and included active and passive ROM measurements, the visual analog scale (VAS) for pain and the disabilities of the arm, shoulder and hand (DASH) questionnaire to assess pain, disability, and quality of life. Improvements over time were assessed using ANOVAs. RESULTS: Thirty-two patients were followed (age: 52 ± 8 years, 25 females, mean symptoms duration of two years). There was a significant improvement in ROM for all amplitudes at day ten (short-term; range: 20-35°, p < 0.001) and at day 180 (long-term; range: 18-47°, p < 0.001). The pain and disability scores significantly reduced by day 180 (mean VAS reduction: 2.6 units, p < 0.001; mean DASH reduction: 9.5 points, p < 0.001). CONCLUSION: Continuous SSNB combined with intensive multidisciplinary rehabilitation represents an efficient therapeutic option for patients with chronic AC who did not respond to conventional treatments.

Return to play decision after shoulder dislocation in upper limb athletes: Critical analysis between the habits of medical professionals and the literature.

BACKGROUND: The return to field is a critical moment for an athlete who has dislocated his shoulder as there is a significant risk of recurrence. The decision to return to field made by the doctor will therefore be crucial for the smooth continuation of the athlete's career. HYPOTHESIS: This objective is to compare the criteria most used by specialists in clearing an overhead athlete to return to competition after a first episode of antero-internal dislocation of the glenohumeral joint with or without surgery and those mentioned in the literature. PATIENTS AND METHODS: The target population consisted of French-speaking physicians in orthopedic surgery, physical medicine and rehabilitation or sports medicine. This study was conducted by the means of a questionnaire. The questionnaire was validated by three experts in sports medicine and published on an online survey website. RESULTS: Sixty-three medical specialists responded to the questionnaire. On average, they use more than nine criteria to decide if an athlete is fit to return to competition. Over the 12 criteria proposed, four are used by more than 90% of respondents: laxity/instability, pain, range of motion and patient's subjective feeling. The methods used to evaluate certain criteria such as pain, joint range or muscular strength are often subjective and very often not validated by the literature. CONCLUSION: Doctors use a set of criteria to allow an overhead athlete to return to competition. This study highlights that the techniques employed to evaluate these criteria are not always thoroughly validated by literature reviews. LEVEL OF EVIDENCE: III; observational study.

Prevention of shoulder injuries in volleyball players: The usefulness and efficiency of a warm-up routine.

OBJECTIVES: The objective of this study was to assess the efficiency of a warm-up routine focused on shoulder injury prevention in volleyball players. DESIGN: Prospective study. SETTING: University. PARTICIPANTS: Eight recreational volleyball teams (44 males, 49 females) were included in the study and assigned to two different groups (prevention or control) in a blinded way. In the prevention group, the players had to perform specific exercises at the beginning of each training session twice a week. MAIN OUTCOME MEASURES: Injuries were recorded monthly in both groups with an online questionnaire. RESULTS: A significant decrease in the total number of injuries as well as in the severity of the injuries was observed in the prevention group in comparison to the control group (p = 0.0001-0.013). For the shoulder, a decrease in injury incidence was also observed in the prevention group. This decrease reached significance in male players (p = 0.045). CONCLUSIONS: The program appears to be efficient to reduce the risk of shoulder injuries in recreational volleyball players. Adjustments in the duration and in the contents of the program will have to be made to further improve compliance and better meet the requirements of both players and trainers.

Differences in strength and fatigue resistance of scapular protractors and retractors between symptomatic and asymptomatic dyskinesis.

CONTEXT: Scapular dyskinesis is a shoulder dysfunction that can be asymptomatic or associated with pain or weakness. Reduced strength and fatigue resistance of the scapular protractor and retractors muscles that stabilize the scapula might contribute to dyskinesis. OBJECTIVE: To determine the strength and fatigue resistance profiles of subjects with symptomatic and asymptomatic scapular dyskinesis, and to compare them to healthy controls using isokinetic assessment. DESIGN: Cross-sectional study. SETTING: University Hospital. PARTICIPANTS: Twenty healthy controls and 21 overhead athletes with symptomatic (n=10) and asymptomatic (n=11) scapular dyskinesis. MAIN OUTCOME MEASURES: Strength (peak torque, maximum work), fatigue resistance (total work) and protraction/retraction ratios measured during a closed-chain isokinetic protocol (40 repetitions in concentric mode at 24.4 cm/s). RESULTS: The scapular protractors' strength and fatigue resistance were significantly higher (p<0.01) in healthy controls (peak torque: 5.0±0.9 N/Kg; maximum work: 2.4±0.5 J/Kg; total work: 72.4±0.6 J/Kg) than in asymptomatic (peak torque: 3.4±0.7 N/Kg; maximum work: 1.7±0.4 J/Kg; total work: 50.0±13.7 J/Kg) and symptomatic (peak torque: 3.8±0.6 N/Kg; maximum work: 1.8±0.3 J/Kg; total work: 58.1±12.9 J/Kg) dyskinetic participants. The dyskinetic symptomatic group presented the highest retractors' strength and fatigue resistance (p<0.01) values (peak torque: 5.2±0.6 N/Kg; maximum work: 2.9±0.8 J/Kg; total work: 87.7±22.7 J/Kg) followed by the healthy controls (peak torque: 4.7±1.0 N/Kg; maximum work: 2.1±0.5 J/Kg; total work: 65.3±17.9 J/Kg) and the asymptomatic dyskinetic participants (peak torque: 3.9±1.0 N/Kg; maximum work: 1.9±0.6 J/Kg; total work: 58.6±18.5 J/Kg). The protraction / retraction ratios showed a gradual decrease (p<0.001) from healthy controls (1.1) to asymptomatic (0.9) and symptomatic (0.7) dyskinetic subjects. CONCLUSIONS: Scapular dyskinesis is characterized by weaker scapular protractors and reduced agonist/antagonist ratios, especially when symptomatic. Targeting the scapular protractors for a better balance of scapular musculature in rehabilitation and strengthening programs may improve shoulder symptoms and function, but more interventional studies are required.

Preseason shoulder screening in volleyball players: is there any change during season?

Background: Volleyball players sollicit their shoulder with high velocity and high ranges of motion. Musculoskeletal adaptations have been described after some years of practice but have not been explored after some months of practice. The objective of this study was to analyze the short-term evolution of shoulder clinical measures and functional performance in youth competitive volleyball players. Methods: Sixty-one volleyball players were assessed twice, at preseason and at midseason. Shoulder internal and external rotation range of motion as well as forward shoulder posture and scapular upward rotation were measured in all players. Two functional tests were also performed: the upper quarter Y-balance test and the Single-arm medicine ball throw. The results obtained at midseason were compared to those measured at preseason. Results: Compared to preseason, an increase in absolute value of shoulder external rotation, total rotation range of motion and forward shoulder posture were observed at midseason (P < .001). An increase in side-to-side difference for shoulder internal rotation range of motion was also observed during the season. As for scapular kinematics, scapular upward rotation was significantly decreased at 45° and increased at 120° of abduction at midseason. Concerning functional tests, an increase in throwing distance in the single-arm medicine ball throw was observed at midseason while no change was noted for the upper quarter Y-balance test. Conclusion: Significant changes in clinical measures and functional performance were observed after some months of practice. Since some variables have been suggested to be correlated to a higher risk of shoulder injuries, the current study emphasizes the importance of regular screening in order to highlight injury risk profiles throughout the season.

Bruxism as a new risk factor of musculo-skeletal disorders?

OBJECTIVES: Musculoskeletal disorders (MSDs), particularly neck and low back pain, constitute a major public health issue worldwide with a heavy morbidity and economic impact. However, the relationships between the stomatognathic system and MSDs are subjected to debate, data sorely lacking. The study objective was to investigate the association between bruxism (BR) and MSDs. Secondary objective includes the study of the association between tooth wear (TW) and MSDs. METHODS: This is a cross-sectional study on 425 participants frequenting a university dental clinic. The presence of MSDs was evaluated with the standardized Nordic questionnaire. The sleep and awake BR assessments were based on clinical examination and self-report. TW was measured with the BEWE index. Socio-demographic factors, medical history, life habits and stress were analyzed as potential confounding variables. RESULTS: 91% of patients reported at least one MSD during the preceding 12 months and 75.5% were diagnosed as bruxers. In multivariate analyses, BR was associated with a 5-fold increased risk of prevalent MSD (OR=5.88 (2.7-12.5), p<0.0001). Regarding TW, for a one-point increase in anterior BEWE score, the risk to present an MSD was increased by 53% (OR=1.53 (1.12-2.08), p = 0.0076). Moreover, BR was independently associated with neck, shoulder, upper back, low back, hip & thigh and knee MSDs. Anterior TW was independently associated with neck, low back and hip & thigh MSDs, and global TW with knee MSDs. CONCLUSIONS: BR and TW were shown to be associated with MSDs. The cause-and-effect relationships between those factors needs to be analyzed to optimize prevention and therapeutic care. CLINICAL SIGNIFICANCE: Results suggest that the body is a whole, a balanced muscular system, where every part constitutes a link of the chain. MSDs management and prevention may require a multidisciplinary team approach and future perspectives include defining the dentist's role in this context, particularly with respect to BR diagnostic and treatment.

Survey of physicians' and physiotherapists' ankle muscle strength assessment practices for safe return to sports after lateral ankle sprain: A short report.

BACKGROUND AND PURPOSE: Ankle muscle strength is an important criterion to consider and assess for return to play (RTP) after lateral ankle sprain (LAS). This study therefore focuses on the reported ankle muscle strength consideration for RTP by physicians and physiotherapists, both clinicians involved in RTP decisions, and how they assess it in daily practice. The primary aim is to compare reported clinical practice on ankle muscle strength evaluation between physicians and physiotherapists. Our secondary aims are: to assess the prevalence of use of qualitative versus quantitative assessment and; to determine if there are any differences in how clinicians with or without a Sports Medicine or Physiotherapy Education approach this assessment. METHODS: A survey on RTP criteria after LAS was completed by 109 physicians in a previous study. A number of 103 physiotherapists completed the same survey. A comparison between clinicians' answers was realized and additional questions on ankle muscle strength were analysed. RESULTS: Physiotherapists consider ankle strength for RTP more than physicians (p < 0.001). A large majority of physicians (93%) and physiotherapists (92%) reported assessing ankle strength manually and less than 10% use a dynamometer. Physicians and physiotherapists with Sports Medicine or Physiotherapy Education selected more quantitative assessment than those without (p < 0.001). DISCUSSION: Despite being recognized as an important criterion, ankle muscle strength is not always part of the RTP criteria after LAS in daily practice. The dynamometers are scarcely used by physicians and physiotherapists, whereas it could accurately quantify ankle strength deficits. Sports Medicine or Physiotherapy Education increases the use of quantitative ankle strength assessments by clinicians.

Preseason assessment of anaerobic performance in elite soccer players: comparison of isokinetic and functional tests.

Isokinetic and functional jump tests are frequently performed for assessing the physical qualities of soccer players during preseason. The purpose of this investigation was to explore, in an elite soccer players population, the relationships between isokinetic strength and functional jump performances. Thirty-eight professional soccer players were evaluated as follows: isokinetic knee assessment in concentric (CON) mode (60, 240°/s) for quadriceps and hamstrings, and in eccentric (ECC) mode for the hamstrings only (30°/s); one-leg hop tests for distance (single hop (SH), triple hop (TH) and triple crossover hop (TCH)); one-leg vertical jump tests (countermovement jump, drop jump). Players with a low bodyweight normalised (BWN) quadriceps (Q) strength (<2.71 Nm/kg) performed, for a majority of the measured variables, significantly reduced jump performances compared to the players with high BWN Q strength (>3.14 Nm/kg; p < 0.05). Greater bilateral differences between uninjured and past injured lower limbs were found with isokinetics (Q CON 60°/s (mean bilateral difference (MBD): 10.3%; p < 0.01), Q CON 240°/s (MBD: 9.9%; p < 0.05), H ECC 30°/s (MBD: 16.1%; p < 0.001) than with functional tests (MBD: 2 to 9%; p > 0.05. In conclusion, due to their complementary role and implications for performance, functional and isokinetic tests should be associated in a preseason soccer players assessment.

The Modified-Athletic Shoulder Test: Reliability and validity of a new on-field assessment tool.

OBJECTIVES: To assess the reliability and the validity of a modified version of the Athletic Shoulder Test (M-AST), using a handheld dynamometer instead of a force plate. DESIGN: Test-retest reliability and concordance between tools. SETTING: University Motion Lab. PARTICIPANTS: Twenty healthy volunteers who practiced an upper limb sport for at least 5 h per week were recruited for the study. MAIN OUTCOME MEASURES: The concordance between the Athletic Shoulder Test (AST) and the Modified-Athletic Shoulder Test (M-AST) was assessed with intra-class correlation coefficients (ICC), paired T-Test and Bland-Altman plots. The inter-session reliability was assessed with intra-class correlation coefficients (ICC), SEM, MDC and paired T-Test. RESULTS: A strong concordance was found between AST and M-AST values (ICC = 0.86-0.97; p > 0.05) in all the positions considered and for both sessions. Bland-Altman plots confirmed these results. However, the inter-session reliability was more variable for both AST and M-AST (ICC = 0.643-0.923; p < 0.05). CONCLUSIONS: The M-AST seems to be a reliable, cheaper and easier to implement alternative to the AST to measure recovery status following matches or training sessions in upper limb athletes. As for the AST, familiarization trials will have to be performed before the assessment to have accurate measurements. CLINICAL TRIALS REGISTRATION NUMBER: NCT05112380.

Sex differences in shoulder performance fatiguability are affected by arm position, dominance and muscle group.

BACKGROUND: Injury prevalence data, muscle strength, and fatiguability differ between males and females. In addition, arm spatial orientation affects muscle activation and strength of the shoulder muscles. Nevertheless, little research has been conducted in relation to the shoulder rotator muscles comparing men and women. Therefore, the main aim of of this study was to perform a comparative investigation between two arm spatial orientations (45° and 90° of abduction in the frontal plane) during a fatigue assessment of the internal rotator (IR) and external rotator (ER) shoulder muscles. Secondly, the interaction between sex and dominance with muscular performance was assessed. METHODS: Forty healthy sedentary participants, 20 males and 20 females took part in this study. Participants performed a fatigue resistance protocol consisting of 30 consecutive maximal concentric contractions of the IR and ER shoulder muscles in a supine position at a speed of 180°/s. The upper limb was abducted to an angle of 45° or 90° in the frontal plane and each participant was tested on the dominant and nom-dominant side, counterbalanced in order of administration. Performance measures of Induced Fatigue (IF; %), Cumulated Performance (C.Perf; J) and Best Repetition (BR; J) were calculated and used for analysis. IF represents the % difference between the amount of work done over the last 3 and first 3 repetitions, BR represents the largest amount of work done during a single contraction, and C.Perf represents the total amount of work done during all repetitions. RESULTS: Muscle group was the only factor to display significant variation when not considering other factors, with higher values for C.Perf (mean difference = 353.59 J, P < 0.0005), BR (mean difference = 14.21 J, P < 0.0005) and IF (mean difference = 3.65%, P = 0.0046). There was a significant difference between both angles, with higher values observed at 90° compared to 45° of abduction for C.Perf by ~ 7.5% (mean difference = 75 to 152 J) and ~ 10.8% (mean difference = 5.1 to 9.4 J) for BR in the ER, in males and females respectively (P < 0.0005). The dominant arm was significantly stronger than the non-dominant arm for C.Perf by 11.7% (mean difference = 111.58 J) for males and by 18% (mean difference = 82.77 J) for females in the ER at 45° abduction. At 90° abduction, only females were stronger in the dominant arm by 18.8% (mean difference = 88.17 J). Values for BR ranged from 9.2 to 21.8% depending on the abduction angle and sex of the athlete (mean difference = 2.44 - 4.85 J). Males were significantly stronger than females by 48.8 to 50.7% for values of C.Perf and BR in both the IR and ER (P < 0.0005). There was a significant difference between the ER and IR muscles, with significantly higher values observed for the IR in C.Perf (mean difference = 331.74 J) by 30.0% and in BR (mean difference = 13.31 J) by 26.64%. DISCUSSION: Differences in shoulder performance fatiguability between sexes are affected by arm position, arm dominance and muscle groups. In agreement with the literature, performance values in males were approximately 50% higher than in females. However, the amount of IF was no different between both sexes. Based on findings in literature, it could be suggested that this is due to differences between males and females in motor control and/or coordination strategies during repetitive tasks. In addition, we also observed the IR muscles to be significantly stronger than the ER muscles. It has long been established in literature that these observations are due to the muscle-size differences between both muscle groups, where the IR muscles can produce a larger amount of force due to the larger cross-sectional area. Results of our study found similar ER:IR ratios compared to previous reports. CONCLUSION: Therefore, these findings are useful for clinicians when monitoring rehabilitation programs in sedentary individuals following shoulder injuries.

The influence of growth and development on shoulder rotators strength in young male and female elite tennis players.

BACKGROUND: Tennis practice requires a lot of technical, physical and mental qualities that have to be trained from the youngest age. The important number of hours spent on the court can lead, medium-to-long term to strength or flexibility adaptations, even in the youngest players. The current study aimed to explore the developmental consequences of repetitively playing tennis on shoulder range of motion and shoulder rotators' strength in elite male and female tennis players. METHODS: Eigthy four painfree elite tennis players were assessed during preseason between 2009 and 2019. Clinical assessment included internal and external rotation range of motion and forward shoulder posture while maximal internal and external rotators strength were assessed with an isokinetic dynamometer in concentric and in eccentric modes (at 60°/s and 240°/s). RESULTS: In male players, growth and maturation induced an increase in forward shoulder posture. Absolute peak torque and bodyweight peak torque of internal and external rotators in concentric and eccentric mode were also significantly increased during with age while ER/IR concentric ratios were significantly decreased. In the female players, only absolute peak torque of internal and external rotators in concentric mode and eccentric strength of external rotators were significantly influenced by the development. CONCLUSIONS: Specific adaptations were found in male and female players with age and practice. The important variability in the results within the different age categories and the gender strengthens the importance of regular screening (and isokinetic evaluations) in young tennis players in order to highlight potential atypical profiles, which could have a negative influence on performance or increase the risk of injuries during the development of the player.

Evolution of the trophy position along the tennis serve player's development.

The trophy position is a coaching cue for the tennis serve that usually corresponds to the racquet high point (RHP) during the preparatory action for the stroke. Mastering this position and its time of occurrence seems essential in overarm movements like in the tennis serve. Clinicians and coaches have a real interest in understanding the trophy position and its evolution during the development of the elite players at different ages. A 3D motion system was used to measure the kinematics of the serve. A group of high-level tennis players were selected for three different age groups: 8 adults (ITN 1), 8 teenagers (ITN 3) and 8 children (ITN 5-6). Results show a modified pattern sequence of the tennis serve between children and adult players. RHP appears earlier relative to impact for children (-0.54 ± 0.10 s) than for adults (-0.36 ± 0.11 s) and teenagers (-0.33 ± 0.05 s) (p = 0.007). At RHP, children present lower trunk transverse plane rotation (p < 0.003) and higher shoulder external rotation (p < 0.003). These positions for the child players may represent an increased risk of shoulder and trunk injury than for older players and contribute to a lower racquet resultant velocity at impact.

Exercise-Based Injury Prevention in High-Level and Professional Athletes: Narrative Review and Proposed Standard Operating Procedure for Future Lockdown-Like Contexts After COVID-19.

In regular times, implementing exercise-based injury prevention programs into the training routine of high-level and professional athletes represents a key and challenging aspect to decrease injury risk. Barriers to implementing such prevention programs have previously been identified such as lack of resources, logistic issues or motivation. The COVID-19 pandemic associated with restrictions on daily life dramatically impacted sports participation from training to competition. It is therefore reasonable to assume that such lockdown-like context has exacerbated the challenge to implement exercise-based injury prevention programs, potentially leading to a greater musculoskeletal injury risk. In this narrative review, recommendations are proposed for building an expertise- and evidence-based Standard Operating Procedure for injury prevention in lockdown-like contexts for high-level and professional athletes. The following recommendations can be provided: (1) assess the global and sport-specific risks in the light of the ongoing cause of isolation; (2) adapt remote training materials and programs; (3) ensure regular quality communication within the staff, between athletes and the staff as well as between athletes; (4) follow the athlete's mental well-being; and (5) plan for a safe return-to-sports as well as for an ongoing monitoring of the load-recovery balance. These key domains should further be addressed to comply with local policies, which are subject to change over time in each individual country. The use of these recommendations may improve the readiness of athletes, coaches, physicians and all sports stakeholders for future lockdown-like contexts.

Tight shoulders: A clinical, kinematic and strength comparison of symptomatic and asymptomatic male overhead athletes before and after stretching.

A tightness of the posterior structures of the throwing shoulder has been hypothesised to be associated with injuries and pain because of alterations of the scapular kinematics and muscular imbalances. The aims of this study were to identify the clinical and biomechanical profile of symptomatic and asymptomatic overhead athletes with a tight shoulder and to evaluate the efficiency of a self-applied stretching program. Twenty male overhead athletes were recruited. Half of them reported a painful shoulder at the beginning of the study. For four weeks, the volunteers performed daily stretching exercises. Before and after the stretching program, gleno-humeral mobility, scapular kinematics, rotator muscles strength and pain were evaluated. Before stretching, the main difference between the groups was more impingement syndrome and rotator cuff tendon lesion positive tests in the symptomatic group (p < 0.027, effect size = 0.51). After the program, pain reported by the symptomatic volunteers was reduced by approximately 40% and the gleno-humeral internal rotation bilateral difference was significantly reduced by 77.6% (p < 0.009, effect size = 0.84). In the symptomatic group, the scapula at rest was significantly more posteriorly tilted (p = 0.027, effect size = 0.69) after the stretching; a position that has been shown to limit the risk of impingement. The absence of significant differences of the profiles of the symptomatic and asymptomatic overhead athletes before stretching may indicate that the initiation of early prevention programs, including self-applied stretching, should not rely solely on biomechanical and clinical parameters and might be recommended to all players with a tight shoulder.

Normalizing gastrocnemius muscle EMG signal: An optimal set of maximum voluntary isometric contraction tests for young adults considering reproducibility.

BACKGROUND: Even though most studies normalize the surface EMG signal of the gastrocnemius muscle using a single position of maximum voluntary isometric contraction (MVIC), several studies tend to indicate that several positions are in fact needed to obtain a maximal voluntary activation (MVA) for most of the subjects. However, no combination of positions has already been described. RESEARCH QUESTION: A combination of MVIC positions to normalize the EMG signal of the gastrocnemius muscle is investigated. the influence of using several positions on the reproducibility of the normalization process is evaluated. METHODS: Twenty healthy volunteers (45 % female - 55 % male, 25.4 years (SD 4.3), 72.6 kg (SD 13.9), 1.78 m (SD 0.12)) were recruited. Six positions for MVIC were compared and the effect of several normalization combinations on a functional task (gait) was evaluated. RESULTS: Several positions are needed to obtain at least 90 % of the MVA for 90 % of the volunteers even though the use of a single well-chosen position (unipodal standing position with knee fully extended and ankle fully plantar-flexed) will lead to no statistically significant differences of the gait evaluation during stance phase. For each position, five repetitions of the MVIC are recommended to obtain a valid MVA. SIGNIFICANCE: This study confirms that using several MVIC positions is recommended when possible to normalize the gastrocnemius muscle EMG signal. However, in the situation of a patient where limited MVIC attempts are possible, using a single well-chosen position should not significantly influence the amplitude and the reproducibility of the measures.

Risk Factors of Overuse Shoulder Injuries in Overhead Athletes: A Systematic Review.

CONTEXT: Shoulder injuries are highly prevalent in sports involving the upper extremity. Some risk factors have been identified in the literature, but consensus is still lacking. OBJECTIVES: To identify risk factors of overuse shoulder injury in overhead athletes, as described in the literature. DATA SOURCES: A systematic review of the literature from the years 1970 to 2018 was performed using 2 electronic databases: PubMed and Scopus. STUDY SELECTION: Prospective studies, written in English, that described at least 1 risk factor associated with overuse shoulder injuries in overhead sports (volleyball, handball, basketball, swimming, water polo, badminton, baseball, and tennis) were considered for analysis. STUDY DESIGN: Systematic review. LEVEL OF EVIDENCE: Level 3. DATA EXTRACTION: Data were extracted from 25 studies. Study methodology quality was evaluated using the Modified Coleman Methodology Score. RESULTS: Intrinsic factors, previous injury, range of motion (lack or excess), and rotator cuff weakness (isometric and isokinetic) highly increase the risk of future injuries. Additionally, years of athletic practice, body mass index, sex, age, and level of play seem to have modest influence. As for the effect of scapular dysfunction on shoulder injuries, it is still controversial, though these are typically linked. Extrinsic factors, field position, condition of practice (match/training), time of season, and training load also have influence on the occurrence of shoulder injuries. CONCLUSION: Range of motion, rotator cuff muscle weakness, and training load are important modifiable factors associated with shoulder injuries. Scapular dysfunction may also have influence. The preventive approach for shoulder injury should focus on these factors.

Activation Profile of Scapular Stabilizing Muscles in Asymptomatic People: Does Scapular Dyskinesis Have an Impact on It?

OBJECTIVE: The aim of the study was to assess the activation profile of scapular stabilizing muscles in dyskinetic asymptomatic people. DESIGN: This is a noninterventional observational study. Two groups of 20 people were included in the study. The first group involved asymptomatic athletes with scapular dyskinesis. The second one included athletes without scapular dysfunction. Muscle activation of upper trapezius, lower trapezius, and serratus anterior were recorded by a surface electromyography during shoulder flexion and shoulder abduction, in unloaded and loaded conditions. RESULTS: A significant increase of the activity of the upper trapezius (between 23% and 31%) and a significant decrease of the activity of the lower trapezius (between 32% and 65%) were observed in the dyskinetic group in comparison with the nondyskinetic group in asymptomatic athletes. A significant increase between 17% and 31% of the activity of the serratus anterior was also observed in dyskinetic people. Likewise, a significant increase approximately 24%-61% and 23%-70% was noted respectively in upper trapezius/lower trapezius and upper trapezius/serratus anterior ratio's in the dyskinetic group. CONCLUSIONS: An alteration of periscapular muscular activation exists in dyskinetic asymptomatic people. Future studies will be needed to know whether those alterations increase the risk of shoulder injuries.

Kinesiotaping for scapular dyskinesis: The influence on scapular kinematics and on the activity of scapular stabilizing muscles.

Scapular dyskinesis is observed in 61% of overhead athletes (Burn et al., 2016). For most of them, it remains asymptomatic. However, scapular dyskinesis is considered a risk factor for shoulder injury by some authors (Clarsen et al., 2014). The aim of this study is to explore the effectiveness of kinesiotaping in modifying scapular kinematics and peri-scapular muscle activity in dyskinetic athletes. The 3-dimensional position and orientation of the scapula as well as the activation of upper trapezius, lower trapezius and serratus anterior were recorded in twenty asymptomatic athletes during shoulder movements (flexion and abduction), in loaded and unloaded conditions and in three circumstances (standard, kinesiotaping 1, kinesiotaping 2). A significant decrease between 9 and 12% in upper trapezius activity was observed with kinesiotaping 1 and 2. Lower trapezius activity was slightly increased with kinesiotaping 1 while it was significantly decreased about 15-20% with kinesiotaping 2. No change was observed in serratus anterior activity, for either kinesiotaping 1 or 2. Considering scapular kinematics, both kinesiotaping 1 and 2 significantly increased posterior tilt and upward rotation. External rotation was decreased with kinesiotaping 2, in comparison to standard condition. Kinesiotaping, and especially taping 1, seems to be an effective method for changing periscapular muscle activity and scapular kinematics.

A foot/ground contact model for biomechanical inverse dynamics analysis.

The inverse dynamics simulation of the musculoskeletal system is a common method to understand and analyse human motion. The ground reaction forces can be accurately estimated by experimental measurements using force platforms. However, the number of steps is limited by the number of force platforms available in the laboratory. Several numerical methods have been proposed to estimate the ground reaction forces without force platforms, i.e., solely based on kinematic data combined with a model of the foot-ground contact. The purpose of this work is to provide a more efficient method, using a unilaterally constrained model of the foot at the center of pressure to compute the ground reaction forces. The proposed model does not require any data related with the compliance of the foot-ground contact and is kept as simple as possible. The indeterminacy in the force estimation is handled using a least square approach with filtering. The relative root mean square error (rRMSE) between the numerical estimations and experimental measurements are 4.1% for the vertical component of the ground reaction forces (GRF), 11.2% for the anterior component and 5.3% for the ground reaction moment (GRM) in the sagittal plane.